Reinforced and Ultraviolet Resistant Silks from Silkworms
Fed with Titanium Dioxide Nanoparticles
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Abstract
As
the perfect combination of strength and luster, silkworm silks
have been widely used in many fields but still need improvements.
This paper demonstrates an <i>in vivo</i> uptake of titanium
dioxide (TiO<sub>2</sub>) nanoparticles by silkworms, leading to the
direct production of intrinsically modified silk. The nanoparticles
can be easily incorporated into the silk gland of silkworm by using
this method due to the interactions between TiO<sub>2</sub> and silk
fibroin molecules. Infrared spectra indicate that TiO<sub>2</sub> nanoparticles
confine the conformation transition of silk fibroin from random coil/α-helix
to β-sheet. Results of synchrotron radiation wide-angle X-ray
diffraction and small-angle X-ray scattering suggest that modified
silks have lower crystallinity, higher mesophase content, and higher
Herman’s orientation functions of crystalline region and mesophase
region than control group. The breaking strength and elongation at
break of the modified silk can be improved up to 548 ± 33 MPa
and 16.7 ± 0.8%, respectively, by adding 1% nanoanatase into
the artificial diet. Moreover, the TiO<sub>2</sub>-1% modified silk
shows well-improved ultraviolet resistant property as the breaking
strength only decreased 15.9% after exposure to ultraviolet light
for 3 h. The <i>in vivo</i> modification method for silkworm
silk is a green, sustainable, and promising route for commercial production
in the future